[llvm] [NFC][indvars] Remove unused code in WidenIV::widenLoopCompare (PR #73506)

[Wenju He via llvm-commits]

wenju-he wrote:

> > @boomanaiden154 Do you have any idea about this error? Thank you
> 
> No, I don't. As long as your tests pass locally, I wouldn't worry too much about the Buildkite failure. In a couple days the infrastructure for that should be getting migrated to Github actions now that Phabricator CI support is going away, so there's not going to be a lot of effort put into fixing these sorts of things on the Buildkite site.

Thank you.

https://github.com/llvm/llvm-project/pull/73506